The present invention relates to an apparatus and a method for recording and/or reproducing data, and more particularly to those capable of performing exact detection of address information or sync information.
For recording data at predetermined positions on tracks of a disk and reading the recorded data from a desired position out of the entire data, it is necessary to record, on the entire tracks, address information which indicates the position each track. In some of optical disks, such address information is recorded by wobbling a track, which is previously formed as a pregroove, correspondingly to the address information. When an access is made to a desired position, the address information recorded by such wobbling is reproduced to thereby specify the position.
Also in some optical disks, a technique of previously forming a predetermined number of sync marks on a pregroove may be contrived to generate a clock signal required for recording and/or reproducing the data. Since such sync marks are formed in a fixed period, clock pulses required for recording and/or reproducing the data can be generated in synchronism with reproduced sync marks.
In this manner, address information or sync information formed previously in a pregroove can be read out by irradiating a laser beam onto a disk and detecting a change of the reflectivity. Accordingly, in a reproduction mode, a laser beam of a fixed intensity is irradiated onto a disk and the data are reproduced from the reflected beam, so that the address information or the sync information can be detected with relative facility as a change of the level.
However, when pits or marks (hereinafter referred to simply as marks) are formed on a track in a recording mode, the intensity of the laser beam is increased and, at any position where no mark is formed, the laser beam intensity is reduced to the same as that in the reproduction mode. As a result, the intensity of the reflection from the disk in the recording mode is changed in accordance with the recorded data (mark-formed position). Therefore, it becomes difficult, particularly in the recording mode, to achieve exact reproduction of the address information or the sync information.